Ingestible vital sign monitor to aid in diagnosis of sleep-related respiratory disorders

A wireless, capsule-like ingestible device can measure multiple vital signs from within the gastrointestinal tract, having the potential to diagnose sleep-related respiratory disorders and capture life-threatening events such as apnoea or opioid overdose, according to a study.

In a first-in-human trial, the device was able to capture the respiratory signal in the 9–25 breaths-per-minute range and the cardiac signal in the 40–95 beats-per-minute range across all 10 participants (mean age 41 years, 90 percent men, mean body mass index 32.9 kg/m²_, 30 percent had either central or obstructive sleep apnoea). [Device 2023;doi:10.1016/j.device.2023.100125]

During a sleep apnoea event in one participant, the device recorded a respiratory signal amplitude that the investigators noted was an indication that the device may be able to detect central sleep apnoea events.

Importantly, the data collected by the device closely matched those collected by standard sleep study metrics. The mean absolute error between the device and polysomnography respiratory rate estimates was 1.0 breath per minute (p<0.001), corresponding to an accuracy of 92.7 percent. For the heart rate estimates, the mean absolute error was 2.5 beats per minute (p<0.001), which translated to a 96.2-percent accuracy.

“What we were able to show is that using the capsule, we could capture data that matched what the traditional transdermal sensors would capture,” said lead study investigator Dr Giovanni Traverso, an associate professor of mechanical engineering at Massachusetts Institute of Technology and a gastroenterologist at Brigham and Women's Hospital both in Massachusetts, US.

“We also observed that the capsule could detect apnoea, and that was confirmed with standard monitoring systems that are available in the sleep lab,” Traverso added.

As for safety, there were no adverse events documented. Results of radiographic imaging taken 14 days after the device was ingested showed successful elimination of the device from the participants’ bodies.

Continuous, unobtrusive monitoring

About the size of a vitamin capsule, the device integrates an accelerometer that measures small ballistic movements in the abdomen that are generated each time the heart beats or breathing occurs. Time stamps and accelerometer data are stored in device memory and periodically transferred to an external receiver for analysis.

“Our device builds on previously reported systems that all require an external component to be worn on the body, which is not practical for long periods of time. Ingestible devices can be designed to reside in the gastrointestinal tract for prolonged periods of time where they are not visible and are completely unobtrusive, thereby allowing for continuous use,” Traverso said. [Sci Transl Med 2016;8:365ra157; Sci Transl Med 2019;11:eaay2602]

The ingestible platform, he added, does away with all the inconvenience of a sleep study, particularly the placement of multiple skin sensors and an overnight observation.

While the ingestible monitoring technology could be used for a variety of applications, Traverso and colleagues are eyeing the device’s application in detecting opioid-induced respiratory depression (OIRD).

“We know that people who have had an overdose are at higher risk of recurrence, so those individuals could be monitored more closely so that in the event of another overdose, someone could help them,” Traverso said.

The next step in the study is to add gastric residency technology, which would enable the device to remain in the stomach for a longer amount of time. Traverso and colleagues are also looking to incorporate an on-demand drug release system that will automatically release an opioid overdose reversal agent when needed.